test: flaky vinyl/errinj_tx.test.lua test

[avtikhon]

Tarantool version:
Tarantool 2.7.0-71-g88b0c86c8f
Target: Linux-x86_64-Debug
Build options: cmake . -DCMAKE_INSTALL_PREFIX=/usr/local -DENABLE_BACKTRACE=ON
Compiler: /usr/bin/cc /usr/bin/c++
C_FLAGS: -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -fopenmp -msse2 -fprofile-arcs -ftest-coverage -std=c11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts -Wno-format-truncation -Wno-gnu-alignof-expression -fno-gnu89-inline -Wno-cast-function-type -Werror
CXX_FLAGS: -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -fopenmp -msse2 -fprofile-arcs -ftest-coverage -std=c++11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts -Wno-format-truncation -Wno-invalid-offsetof -Wno-gnu-alignof-expression -Wno-cast-function-type -Werror

OS version:
Debian 9

Bug description:
https://gitlab.com/tarantool/tarantool/-/jobs/862915919#L4451

artifacts.zip

results file checksum: 0f9de3eaa09260df452704d431a174b9

[034] --- vinyl/errinj_tx.result	Fri Jun  5 06:51:39 2020
[034] +++ var/rejects/vinyl/errinj_tx.reject	Fri Nov 20 12:09:10 2020
[034] @@ -465,7 +465,7 @@
[034]  ...
[034]  itr.next()
[034]  ---
[034] -- [1]
[034] +- [10]
[034]  ...
[034]  c = txn_proxy.new()
[034]  ---
[034] @@ -476,7 +476,7 @@
[034]  ...
[034]  c('s:get(1)')
[034]  ---
[034] -- - [1]
[034] +- 
[034]  ...
[034]  -- Resume the first transaction and let it fail on WAL write.
[034]  errinj.set('ERRINJ_WAL_WRITE', true)
[034] 

Steps to reproduce:

Optional (but very desirable):

• coredump
• backtrace
• netstat